1. Field of the Invention
The present invention relates to a wireless communication apparatus and method, and a computer program, for transmitting and receiving a wireless communication signal, and more particularly to a wireless communication apparatus and method, a computer program, capable of data transmission and distance measurement.
2. Description of Related Art
More specifically, the present invention relates to a wireless communication apparatus and method, and a computer program, in which ranging of a distance between wireless apparatuses is performed on the basis of a time from a packet transmission to a packet reception, and more particularly to a wireless communication apparatus and method, and to a computer program, which compensates for timings or a delay time between a data signal and a clock signal.
A wireless LAN has drawn attention as a system capable of releasing users from LAN wirings of a wired type. Wireless LAN can omit most of cables in a work space of an office and the like so that communication terminals such as personal computers (PC) can be moved relatively easily. Demands for wireless LAN is increasing greatly because of recent tendency of higher speed and lower cost required in wireless LAN systems. Introducing a personal area network (PAN) has been studied recently in order to configure a small scale wireless network of an plurality of electronic apparatuses installed in a personal area and perform information communication. For example, different wireless communication systems and apparatuses are defined by using frequency bands whose license by a supervisory office is not necessary, such as 2.4 GHz band and 5 GHz band.
For example, a wireless communication scheme called “ultra wide band (UWB) communication” for transmitting information carried by a faint impulse sequence has drawn attention as a wireless communication system realizing near field ultra high speed transmission, and this scheme is expected to be used in practice. As an access control method for ultra wide band communication, a data transmission scheme of a packet structure including a preamble is currently devised in IEEE 802.15.3 and the like.
UWB communication has a high temporal resolution if an ultra narrow pulse is used. By utilizing this property, “ranging (distance measurement)” for radar and positioning becomes possible. Recent UWB communication can provide both high speed transmission in excess of 100 Mbps and an inherent ranging function (e.g., refer to Japanese Translation of PCT International Application (KOHYO) No. 2002-517001 (Patent Document 1)).
It is anticipated that a wireless personal access network (WPAN) for near field communication (NFC), typically UWB, is configured for a variety of electronic home appliances and consumer electronics (CE). It is therefore considered that value added wireless communication in addition to high speed data transmission is to be realized by utilizing position information through ranging, such as navigation and near field communication. It is considered that a ranging function in addition to high speed data transmission is desired to be implemented.
Generally, a ranging system of this type measures a distance on the basis of a time from a packet transmission to a packet reception. A range target apparatus only returns a received signal after carrying out almost no processing on it. As an example, the range target apparatus returns a signal sent from a ranging wireless apparatus by superposing upon it information relating to the range target apparatus. The ranging wireless apparatus measures a distance by measuring a turn-around radio wave propagation time (for example, refer to Japanese Patent No. 3118578 (Patent Document 2)). There is, however, another method by which a ranging apparatus measures a distance on the basis of a time from a transmission to a return signal reception from a range target apparatus, the time including the signal processing times in the ranging apparatus and the range target apparatus (for example, refer to Published Japanese Patent Application (KOKAI) No. 2001-183447 (Patent Document 3), Published Japanese Patent Application (KOKAI) No. 2001-50147 (Patent Document 4) and Published Japanese Patent Application (KOKAI) No. HEI-8-62334 (Patent Document 5)).
In this ranging system measuring a distance between wireless apparatuses on the basis of a time from a packet transmission to a packet reception, the time includes the signal processing times in the ranging apparatus and the range target apparatus. It is therefore necessary to compensate for timings or a delay time between a data signal and a clock signal, when the data signal is transmitted.
A delay between a data signal and a clock signal is roughly classified into a delay within one clock period and a delay over one clock period.
For example, elastic store operation has been proposed which can perform data transmission correctly at all clock timings (for example, refer to Published Japanese Patent Application (KOKAI) No. HEI-9-139730 (Patent Document 6)).
A data transmission apparatus has been proposed (for example, refer to Published Japanese Patent Application (KOKAI) No. HEI-10-210018 (Patent Document 7)). According to this apparatus, a data signal is synchronized with a clock signal having a constant period, and the data signal and the clock signal are transmitted from a transmission side to a reception side via a transmission route. In this case, a relative delay amount between the data signal and the clock signal can be set reliably in an allowable range, and a variety of routes can be adjusted independently.
An interface circuit has been proposed which automatically adjusts a variation in a data transmission delay time to retain a phase for correctly receiving data (for example, refer to Published Japanese Patent Application (KOKAI) No. 2001-251283).
However, all of the above-described techniques adopt the configuration that data is delayed relative to the clock to the position where the data can be correctly acquired, when data is transferred synchronously with the clock. In other words, only a delay in one clock period is compensated, and a delay over one clock period is not processed specifically so that a delay amount relative to the clock cannot be compensated in a synchronizing system.
A ranging communication apparatus cannot determine whether data is delayed one period or longer relative to a clock so that correct ranging cannot be realized.
The present invention provides an excellent wireless communication apparatus and method, and a computer program, capable of both data transmission and distance measurement (ranging).
The present invention also provides an excellent wireless communication apparatus and method, and a computer program, capable of proper ranging between wireless communication apparatuses on the basis of a time from a packet transmission to a packet reception.
The present invention further provides an excellent wireless communication apparatus and method, and a computer program, capable of compensating for timings or a delay time between a data signal and a clock signal when the data signal is transmitted.
The present invention has been made in consideration of the above-described issues. According to a first aspect of the present invention, there is provided a wireless communication apparatus for transmission/reception of a wireless communication signal, comprising:
first and second circuits for processing a transmission/reception signal;
an oscillator for generating a reception clock on a first circuit side, the reception clock being used for an operation reference;
a first interface for supplying the reception clock from the first circuit to the second circuit;
a second interface for inputting, to the first circuit, transmission data output from the second circuit synchronously with the reception clock supplied from the first circuit; and
delay compensating means for compensating for a delay between the reception clock and transmission data at the first circuit, the reception clock and transmission data being input via the second interface.
For example, the first circuit may be a wireless circuit module for performing a transmission/reception process of a wireless communication signal and the second circuit may be a physical layer module for processing transmission data in a physical layer protocol.
In a ranging system measuring a distance between wireless apparatuses on the basis of a time from a packet transmission to a packet reception, the time includes the signal processing times in a ranging apparatus and a range target apparatus. It is therefore necessary to compensate for timings or a delay time between a data signal and a clock signal, when the data signal is transmitted.
A delay between a data signal and a clock signal is roughly classified into a delay within one clock period and a delay over one clock period. Although a related art data transmission apparatus can compensate for a delay in one clock period, a delay over one clock period is not processed specifically.
The wireless communication apparatus of the present invention is provided with the delay compensating means for compensating for a delay between the reception clock and the transmission data at the first circuit, the reception data and transmission data being input via the second interface. This delay compensating means inserts a proper delay amount into the transmission data and maintains a delay of the transmission data to be always constant to thereby compensate for the delay time.
The wireless communication apparatus of the present invention is provided with a data transmission mode for executing a data transmission process and a calibration mode for compensating for a delay time of transmission data.
In the calibration mode, the delay compensating means sends a calibration pulse having a duration over an anticipated maximum delay time from the first circuit to the second circuit via the first interface, and compensates for a delay time on the basis of a delay between a pulse looped-back from the second circuit to the first circuit via the second interface and the original calibration pulse.
In accordance with a phase difference between the pulse looped-back from the second circuit to the first circuit via the second interface and the original calibration pulse, the delay compensating means compensates for a delay time less than one clock period. A proper delay amount is inserted into transmission data to make the transmission data have the maximum delay time.
As described above, according to the present invention, even if the first and second interfaces operate at a high speed clock, correct data transmission is possible irrespective of a variation in a data delay amount.
Further, a variation in a data transmission time per clock unit to be caused by a variation in a sampling position of the clock due to a data delay amount can be fixed to a predetermined constant value. Data transmission sensitive to a time fluctuation is therefore possible.
According to a second aspect of the present invention, there is provided a computer program written in a computer readable format so as to make a computer system execute a process for allowing a wireless communication apparatus to perform delay time compensated data transmission, the wireless communication apparatus comprising first and second circuits for processing a transmission/reception signal, an oscillator for generating a reception clock on a first circuit side, the reception clock being used for an operation basis, a first interface for supplying the reception clock from the first circuit to the second circuit, and a second interface for inputting, to the first circuit, transmission data output from the second circuit synchronously with the reception clock supplied from the first circuit, the computer program comprising the steps of:
sending a calibration pulse having a duration over an anticipated maximum delay time from the first circuit to the second circuit via the first interface;
compensating for a delay time in one clock period in accordance with a phase difference between a pulse looped-back from the second circuit to the first circuit via the second interface and the original calibration pulse; and
inserting a proper delay amount into transmission data to make the transmission data have a maximum delay time.
The computer program according to the second aspect of the present invention is a computer program written in a computer readable format so as to make a computer system execute a predetermined process. In other words, by installing a computer program according to the second aspect of the present invention in a computer system, the computer system achieves cooperative operations so that it is possible to obtain operations and effects similar to those of the wireless communication apparatus according to the first aspect of the present invention.
According to the present invention, it is possible to provide an excellent wireless communication apparatus and method, and a computer program, capable of both data transmission and distance measurement.
Further, according to the present invention, it is possible to provide an excellent wireless communication apparatus and method, and a computer program, capable of proper ranging between wireless apparatuses in accordance with a time from a packet transmission to a packet reception.
Furthermore, according to the present invention, it is possible to provide an excellent wireless communication apparatus and method, and a computer program, capable of compensating for timings or a delay time between a data signal and a clock signal when the data signal is transmitted.
According to the present invention, for data transmission synchronous with a clock, a clock signal and a signal synchronous with the clock signal can be transmitted to a communication partner. Conversely, when the signal synchronous with the clock signal is received at the communication partner, data can be synchronized with an original own clock signal of the communication partner, irrespective of a data delay amount at the transmission side. In this case, a delay can be adaptively inserted by measuring the delay amount at the transmission side in order to make the own data delay amount constant irrespective of the delay amount at the transmission side.
Other objects, features and advantages of the present invention will become apparent from more detailed description when read in conjunction with embodiments of the present invention to be described later and accompanying drawings.